I just ordered a book that the WL is REALLLLY long but I looked under the author's name and it showed that a version of the book was available.  So I ordered it.  Well the isbn is only 6 characters long.  Is this a book that has been posted without an isbn?   

Yes, that's a non-ISBN posting.  The 6 digit code is PBS's "in house" version of an ISBN, so the PBS Database can still track the item.  I've ordered TONS of books like that, preferring older editions printed before the age of ISBN coding.  If the edition you get isn't all that important to you, it sounds as if you've found your book without the wait :)

Thanks James! Yeah, I really don't care about the edition I get...I just wanted to read the book.  But when I saw the isbn it got me wondering.

Aaron, that's a 'short' ISBN.  Like posted above, they are a one-time PBS number assigned to books posted without true ISBN numbers.  Or other reasons, such as the poster had a book that didn't match the binding listed for their book...stuff like that.  If it's the title and author you want, good for you!!